Odd thing in back of my throat?

Recently, I've had a lot of phlegm in the back of my throat, and bad breath. Today I had mucus in my saliva (I noticed after I was done brushing my teeth). Just a while ago, I actually looked into my throat and noticed that on the right side of my mouth, behind my uvula, and to the right, it looks swollen compared to the other side. I have no clue how long its been swollen like that, does anyone know what it is?